This invention relates to fail over in a cluster system.
Nowadays companies and other organizations' operations rely more heavily than ever on computer systems, and shutdown of a computer system can thus cause a serious damage to the organization. Cluster system is one of technologies developed to avoid such total shutdown of a computer system.
A cluster system is a system composed of plural computers (also called as nodes) that are connected to one another in groups (clusters). Load-balancing systems and fail over systems, for example, are known cluster systems.
A fail over cluster system is a system which uses plural computers to obtain redundancy. For instance, in the case where a server that provides an business application service to client computers is a cluster constituted of two computers, when an operation of the business application that has been processed by one of the two computers shuts down by a failure or the like, the active computer is taken over by the other computer, so the client computers can continue to receive the service.
The client computers view the whole cluster as one computer, and therefore cannot tell which computer is providing the service after the operation is taken over (after the fail over is executed).
If such a fail over cluster system executes fail over without taking into consideration the running state of a fail over computer to which the operation is handed over, the response speed of the fail over computer could be lowered by too much load from the fail over. Techniques with which the order of priority in fail over can be changed according to the running state of a fail over computer have been disclosed (for example, JP 11-353292 A).